The increased use and reliance on computers, electronics, and other electrical driven devices demand that power be available under all operating conditions. This requirement is paramount when the application is for an aircraft or helicopter, for obvious safety of flight reasons. As an example, the most advanced helicopters being developed are utilizing `fly-by-wire` systems. These systems centralize flight control in a series of computers linking pilot inputs to control, and utilize electrical driven actuators as opposed to a direct link using cables, pulleys, and hydraulic pressure for primary control. In such systems it is critical that the electric power generation be maintained over all operating conditions to ensure maintenance of proper control over the aircraft.
For a fly-by-wire helicopter system electric power sufficient to control flight surface motion is required whenever the rotor is capable of supplying a force strong enough to actually move the helicopter. For a typical system this occurs as low as approximately twenty percent of rated rotor speed. Prior systems have utilized an electronic power converter in addition to a battery in an attempt to supply the power required for the fly-by-wire systems. While such a system is possible, the added weight and increased size of a battery capable of supplying enough power to the fly-by-wire systems for an extended period is prohibitive. Additionally, such a system has a limited time of operation due to the discharge characteristics of the battery, and the battery is negatively effected by the temperature extremes at either end of the flight envelope.
Another system architecture which has been considered for similar applications utilizes a permanent magnet generator directly driven by the main rotor gearbox. This system is adversely affected by the large speed range. To meet system power requirements under all operating conditions, the permanent magnet generator must be sized at the twenty percent speed condition. At normal operating speeds, however, excessive voltage or power is generated. This excess power must be purged as heat, and directly decreases the amount of energy available to the lift generating rotor.
Another system architecture which has been considered for similar application utilizes a hydraulic driven permanent magnet generator that is connected to the flight critical hydraulic circuit that actuates the rotors. This system, however, also extracts energy from the lift generating rotor. The hydraulic driven permanent magnet generator additionally must be sized far the extremes of temperature. This defines the flow which must be continuously extracted from the flight critical hydraulic circuit during all phases of flight which will effect the performance and efficiency of the system as a whole.
The helicopter, however, utilizes a gearbox which operates to change the speed and torque from the engine to turn the rotor. It is a principle objective of the instant invention, therefore, to provide a gearbox which includes, integral therewith, a new and improved electric power generation system. More specifically, it is a principle objective of the instant invention to utilize the teeth of a rotating gear which meshes with other gears within this gear box as salient poles forming a switched reluctance rotor. This will allow generation of electric power in the environment and temperature ranges of the mechanical gearbox without the addition of a separate generator and the associated loss in overall system efficiency. Additionally, this gearbox will provide a controlled output power regardless of the speed of the gears driving the rotor.
In addition, computers and other critical control electronics are also utilized in other types of systems which would be equally adversely affected by a sudden loss of power to their control circuitry. In these systems, such as chemical processing, nuclear processing, mining, manufacturing, etc., a back-up or emergency source of power is required to provide power to allow a controlled shutdown of the affected equipment, or to allow continued operation during the power loss event. One way to provide this emergency power is to utilize a stand-by generator which will cut-in when the primary source goes off line. This type of system is inefficient, however, because the generator must be running at all times to prevent a power loss event. Other systems utilize a battery to provide emergency power, but batteries have a limited life, require periodic maintenance, and are adversely effected by temperature extremes.
It is therefore a further object of the instant invention to provide a mechanical drive system utilized in such processing, mining, manufacturing, etc., which will additionally provide continuous electric power during operation of the drive system. This will allow continued controlled operation of the drive system during the main power loss event, or may allow a controlled shutdown of the drive system under power if desired. The instant invention, therefore, is directed at overcoming these and other problems present in the prior art.